Only ego can only attack itself. It cannot attack what is not inside of itself.
If you are outside of the ego, you cannot be attacked. You are immortal and invulnerable.
If you identify with ego, labeling your sense of self as being "made of" something ego .... sin, guilt, fear, sickness, unworthiness, etc... then you can be attacked. Because THAT illusion can be attacked, because it IS attack.
The ego can only attack that which is PART OF its thought system. It is like a dog which runs wild in a yard, barking and screaming, threatening to bite, but the yard is fenced in, and so long as you are not inside the fence, the dog can do nothing.
Identifying with/as something illusory, ie ego, you put yourself inside the yard. Now your "self" is inside the realm of the ego's thought system. And it will attack you, because all illusions are thoughts of war. The ego is a mindset of self-attack, inner conflict, a war with yourself.
The Kingdom of God is outside of the realm of the ego, or rather, the ego is nowhere that God's Creation is. The Kingdom of God therefore cannot be attacked. The mind of the ego cannot enter Heaven. As soon as it approaches the light it is dispelled and dissolved.
Darkness cannot exist where there is light. And the ego "self" cannot be taken into the light, or into heaven. Trying to do so will merely make it either resist or pretend that it is becoming spiritual. Darkness has no effect on light, but the belief that darkness can hide light is part of the ego's insanity.
So if you want to be immortal, all you need to do is recognize your identity has nothing to do with ego, is not made of ego in any way, has no illusions in it, and is outside of the ego thought system. Then you cannot be touched.
There is then NOTHING the ego can do to attack you or hurt you, to make you sick, to make you die, to make you suffer in any way. You are utterly OUT OF REACH. You cannot be sick or die and you do not depend whatsoever on the ego's forms of supply or sustaining of life. You are sustained by the love of God. The love of God doesn't just warm your heart amidst a dreary world, it POWERS YOU and PROTECTS YOU.
What is innocent and sinless cannot be sinned against. Perfect invulnerability is not only possible is the ONLY real possibility.
Immortality is permanent and real. Mortality is a lie. Immortality is not an exception, it is perfectly natural. Mortality is UNNATURAL.